Show the neoirc-cli screen without waiting at start-up (closes #226)

Run added the start-up status bar and welcome lines through
SetStatus and AddStatus before it started the tview event loop. Both
wait for that loop, so neoirc-cli stopped before it showed its
screen. They now run on a goroutine, as typed lines do.

Run now passes a new UI to run, which holds the start-up path and
returns its error. TestStartUp calls run with a simulation screen. It
fails unless, within five seconds, the status window holds two lines:
first the one with "Welcome to neoirc-cli", then the /connect hint.

Model: opus-5-5

internal/cli/app.go

@@ -34,30 +34,44 @@ type App struct {
 
 // Run creates and runs the CLI application.
 func Run() {
-	app := &App{ //nolint:exhaustruct
+	err := run(NewUI())
-		ui:   NewUI(),
-		nick: "guest",
-	}
-
-	app.ui.OnInput(app.handleInput)
-	app.ui.SetStatus(app.nick, "", "disconnected")
-
-	app.ui.AddStatus(
-		"Welcome to neoirc-cli — an IRC-style client",
-	)
-	app.ui.AddStatus(
-		"Type [yellow]/connect <server-url>" +
-			"[white] to begin, " +
-			"or [yellow]/help[white] for commands",
-	)
-
-	err := app.ui.Run()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 		os.Exit(1)
 	}
 }
 
+// run starts the client on ui and returns when ui stops. Tests
+// call it with ui on a simulation screen.
+func run(ui *UI) error {
+	app := &App{ //nolint:exhaustruct
+		ui:   ui,
+		nick: "guest",
+	}
+
+	app.ui.OnInput(app.handleInput)
+
+	// SetStatus and AddStatus wait for the event loop, which
+	// app.ui.Run starts below, so they run on a goroutine. The
+	// nick is read first, as a typed /nick may change app.nick.
+	nick := app.nick
+
+	go func() {
+		app.ui.SetStatus(nick, "", "disconnected")
+
+		app.ui.AddStatus(
+			"Welcome to neoirc-cli — an IRC-style client",
+		)
+		app.ui.AddStatus(
+			"Type [yellow]/connect <server-url>" +
+				"[white] to begin, " +
+				"or [yellow]/help[white] for commands",
+		)
+	}()
+
+	return app.ui.Run()
+}
+
 func (a *App) handleInput(text string) {
 	if strings.HasPrefix(text, "/") {
 		a.handleCommand(text)

internal/cli/app_internal_test.go

@@ -4,6 +4,8 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"slices"
+	"strings"
 	"testing"
 	"time"
 
@@ -22,13 +24,22 @@ const (
 )
 
 // eventLoopTimeout is how long a test waits for a typed line to
-// be handled, or for the UI to stop, before it fails.
+// be handled, for the welcome lines, or for the UI to stop, before
+// it fails.
 const eventLoopTimeout = 5 * time.Second
 
 // holdTime is how long TestLinesKeepOrder holds the first line,
 // which gives the second line time to start too early.
 const holdTime = 200 * time.Millisecond
 
+// welcomeLines is the number of lines run adds to the status
+// window when the client starts.
+const welcomeLines = 2
+
+// checkInterval is how often TestStartUp reads the status window
+// while it waits for the welcome lines.
+const checkInterval = 10 * time.Millisecond
+
 func TestMemberPrefix(t *testing.T) {
 	t.Parallel()
 
@@ -348,6 +359,78 @@ func TestLinesKeepOrder(t *testing.T) {
 	waitHandled(t, handled, secondLine)
 }
 
+// TestStartUp runs the client's start-up path on a simulation
+// screen. It fails unless the event loop starts and the status
+// window gets two lines: first the one that holds "Welcome to
+// neoirc-cli", then the /connect hint.
+func TestStartUp(t *testing.T) {
+	t.Parallel()
+
+	ui := NewUI()
+	ui.app.SetScreen(tcell.NewSimulationScreen(""))
+
+	// One slot, so that run's goroutine can end even after the
+	// cleanup below has stopped waiting for it.
+	done := make(chan error, 1)
+
+	go func() { done <- run(ui) }()
+
+	t.Cleanup(func() {
+		ui.Stop()
+
+		select {
+		case err := <-done:
+			if err != nil {
+				t.Errorf("run: %v", err)
+			}
+		case <-time.After(eventLoopTimeout):
+			t.Error("run did not return after the UI was stopped")
+		}
+	})
+
+	// run adds the welcome lines on a goroutine, so the status
+	// window is read until it holds two lines. Each read waits for
+	// the event loop, so the reads run on a goroutine too, which
+	// this test stops waiting for after eventLoopTimeout. The
+	// channel has one slot, so that goroutine can still end.
+	shown := make(chan []string, 1)
+
+	go func() {
+		for {
+			var lines []string
+
+			ui.app.QueueUpdate(func() {
+				lines = slices.Clone(ui.getOrCreateBuffer("(status)").Lines)
+			})
+
+			if len(lines) == welcomeLines {
+				shown <- lines
+
+				return
+			}
+
+			time.Sleep(checkInterval)
+		}
+	}()
+
+	var lines []string
+
+	select {
+	case lines = <-shown:
+	case <-time.After(eventLoopTimeout):
+		t.Fatalf("the status window did not get the welcome lines within %v",
+			eventLoopTimeout)
+	}
+
+	if !strings.Contains(lines[0], "Welcome to neoirc-cli") {
+		t.Errorf("first status line is %q, want the welcome line", lines[0])
+	}
+
+	if !strings.Contains(lines[1], "/connect <server-url>") {
+		t.Errorf("second status line is %q, want the /connect hint", lines[1])
+	}
+}
+
 // TestOwnEventFromOtherClient checks that a message, notice,
 // join or part that the user's session makes from another
 // client shows as one line in the buffer it belongs to.